Modes & Keys

An example of what I need to know is if I write a song in the key of Fmaj. I want a different sounding solo, something that stands out but will also work with the rhythem notes in Fmaj. I hear all this talk about Modes and how they work in any key. I also hear the Phrygian Mode has a very unique sound. So if I want it to fit in the key I would use A# Phrygian right?
But the thing is it's the exact same scale with a different root note, that dosen't help at all for a different sounding solo because it's the same scale. Anyway I was wondering if I have this right or if I should be using F Phrygian instead?
And finally what other scales should I learn that would portray an interesting sound but still work if I use the notes in the Fmaj scale as my rythem?

They are the same 7 notes, no matter what mode you play, but it is the chord they are played over that gives them their character. For example, your song, its in the key of F maj. The notes in F major are F G A Bb C D and E. If you want to use the Phrygian mode then you play the mode that goes from A to A, over an A minor chord. I don't know where you got A# from. In the key of Fmaj there isnt an A# - it's a Bb (to avoid confusion with A natural), and the mode would be Lydian, not Phrygian.